The design of rotary flow machines, especially a gas turbine, requires end-to-end mounting of components which are stationary and/or moving relative to one another. For functional reasons, one or more open cavities or gaps, over which in case of a turbine a hot gas flow flows in the hot gas path of the turbine, often remain between these components. Penetration of the hot gas into open cavities between components must be avoided at all costs on account of the high temperatures of the hot gas, which are often even higher than the maximum permissible material temperatures. Hot gas, which nonetheless penetrates into the cavities, as a consequence of the heat exchange with the components adjacent to the cavities, may therefore lead to inadmissibly high temperatures of these components. This in turn is the reason of component damage, in particular in the form of component cracks or an at least marked reduction in the service life of these components.
Typically these open cavities have been sealed against the hot gas penetration by means of mechanical seals such as, for example, seal plates and seal strips, bellows and spring-loaded seals or even by means of arrangements for fluid-dynamic sealing. Mechanical seals, on account of their contacting operating principle, are subjected to abrasive wear and consequently have only a limited service life.
Described in Patent Specifications GB 855 040 and U.S. Pat. No. 3,645,544 are sealing arrangements in which, in order to seal a gap against hot gas penetration, a secondary fluid is supplied into the gap in such a way that a vortex system forms in the gap. However, the sealing arrangements described in each case can be used only for gaps between two components where the components rotate relative to one another and the gaps in each case extend over the entire periphery.
A further known arrangement for sealing a gap against hot gas penetration is disclosed in EP 1 347 153 B1 in which a vortex flow is generated by feeding additional air into the gap between two axially adjacent components each bordering at least partially the hot gas path of a gas turbine. In a preferred embodiment inside the gap in shape of a one side open cavity a chamber is arranged in the longitudinal direction of the gap which is designed as a rotary chamber having a circular or elliptical cross section into which supply conduits merge through which air is injected approximately tangential relative to the vortex flow within the vortex chamber. The sealing function of the arrangement bases on the intense air vortex inside the gap which prevents the hot gas to enter the gap.
WO2009/083456 A1 describes a gas turbine with cooling ports distributed around circumference through which cooling air is injected into the hot gas flow of the combustion chamber outlet. In order to improve the flow conditions in the hotgas in such a gas turbine, the cooling air ports are subdivided into a first group of cooling ports which corresponds to the arrangement of guide vanes and a second group which corresponds to the arrangement of the burners.
Those known solutions using a blocking air flow injected into the gap so that hot gas is purged out of the gap air have the disadvantage of a high air consumption which causes high operating costs and decreasing total efficiency of such a rotary flow machine.
EP 1 741 877 A1 describes a turbine thermal heat shield and a guide vane for a gas turbine with an open cavity between the two adjacent components. The heat shield element has in downstream direction a perpendicular bent wall with cooling bores (FIG. 4, FIG. 7). Between said perpendicular wall and the supporting structure of the combustion chamber with the heat shield is a residual gap arranged which allows a movement of the wall and a closing of the gap during operation.
Document EP 0 902 164 A1 describes a platform cooling having a guide-blade platform which is subjected to a hot gas stream and is separated by a gap from a combustion chamber segment arranged upstream, one or more segment cooling bores being arranged in the combustion chamber segment. The segment cooling bores connect a cooling air chamber to the gap. The guide-blade platform has a surface on the downstream side in the region of the gap, the axes of the one or more segment cooling bores (multiple bores are arranged one after another in circumferential direction) running roughly tangentially to said surface. That means special geometric cavity features are required. The described platform cooling arrangement is advantageously used for gaps with widths of less than 5 mm, preferably less than 2 mm. In FIG. 3 of EP 0 902 164 A1 is shown that the segment cooling bores and the platform cooling bores are arranged alternately so as to be staggered relative to one another along the circumference.